Process of rolling tubes and rods



Nov. 10, 1936. w. J. ASSEL PROCESS OF ROLLING TUBES AND RODS 2 Sheets-Sheet 1 2 Fa F 2, 4/ F I 0 e 0 6 5 2 5 C C I \v..\ 5 5 W1 A l. :11 3A 3 O E/ D 11/5 firm/was NOV. 10, 1936. w J ASSEL 2,060,767

PROCESS OF ROLLING TUBES AND RODS Filed Feb. 15, 1933 2 Sheets-Sheet 2 Patented Nov. 10, 1936 PROCESS OF ROLLING TUBES AND RODS Walter J. Assei, Canton, Ohio, assignor to The Timken Roller Bearing Company, Canton, Ohio, a corporation of Ohio Application February115, 1933, Serial No. 656,899

11 Claims'.' (01. 80-62)" According, to present day practice, metal tubes and rods, particularly light wall seamless tubes are producedby reducing the section of a larger sized tube or solid by passing it back and forth I through successive roll stands, each pass reducing' the piece slightlyuntil the'desired section is obtained. In the case of tubing, this longitudinal rolling is done on the rough tube which has previously been produced in any manner as onthe piercing mill or piercing press; and a plug, which isheld in position by a mandrel bar, is located in the opening between the rolls, the tube being rolled over thisstationary plug, thereby reducing the outside diameter or the wall thickness or both. A rather small reduction only can be made at each'pass due to the following limitations; overfilling pass groove causing fins, limitation of the bite of the rolls, and resistance to longitudinal feed due' to friction of the plug. The number of passes possible is limited by the loss of heat.

Another serious defect incident to present day practice is scoring of the interior surface of the tube caused by slag galling, between the stationary plug and the tube wall. Besides, the roll cost and lost time due to changing rolls are excessive as each size rolled requires'a-separate passan'd'the number of grooves in one set of rolls islimited. The number of passes possible is limited by the loss of heat. The maximum possible elongation on one heat is two to one, withthe usual ratio about one and one-half to one. Further reduction requires a second reheating with consequent scale loss. Again, said practice does notproduce a finished tube as a' slight ridge is usually produced at the parting of the rolls which must be'rolled out inthe reeling machine. Again, this type of longitudinal rolling does not correct the initial eccentricity of the bore of the work piece but under certain conditions may aggravate it in the finished piece.

The principal objects of the present invention are to devise a process which will accomplish a greater reduction on one heating with minimum scaling, which willfproduce a superior product with a better finish, which can produce smaller tubes than is possible by the previous method, which can eliminate the usual separate reeling operation, and which may be carried out at less cost. h

The invention consists principally'in simultaneously rotating the work on its own axis, moving it' longitudinally and rolling or displacing the metal by a surface on the "work roll which is at a steep angle to the direction of feed of the "of the work piece'through the mill and work piece. The invention further consists in a roll for carrying out said process, particularly characterized by having a conical working shoulder disposed at a steep angle to .the line of feed. The invention further consists in the process and operations and in the roll hereinafter described and claimed.

In the accompanying drawings,:wherein like reference numerals-refer to like parts wherever they occur, I

Fig. 1 is a top plan view of a group of rolls for carrying out my invention,

Fig. 2 is a longitudinal sectional view along the line of contact of one roll with 'the work tively, in Fig. 4.

A preferred form of the mill diagrammatic'ally illustrated in said drawings is the subject matter of my copending application forpaten Serial No. 727,934 filed May 28, 1934.

For the purposes of this description, the 10m gitudinal center line of the work piece I as it passes through the mill is regarded as theaxis of the mill; Rotatably mounted work rolls 2 (preferably three in number) are arranged at equal distances apart from this axis, with their own axes converging in the direction of travel of the workpiece, indicated by an arrow. The' work rolls- 2 are'of larger diameter at the end '3 where the work piece enters (herein called from end) than at the end lwhere the work piece leaves (herein called rearend). While the axes of the work rollsconverge rearwardly, they are all somewhat inclined with relation to intersecting planes through the axis of the machine; that is, they' will not meet onthe axis but are skewed'with relation to the axis of the mill. This "angle determines the rate of'feed hence is designated as the feed angle.

Each of the work rolls 2 is of generally conical form with its surface divided into zones with different functions. The first zone A, being the zone at the front or large end of the "roll, is preferably anarrow zone of cylindrical shape "which, in cooperation with like zones on the other work rolls, serves to facilitate the entry of the end of the work piece I between therolls.

-The next adjacent zone B is of conical form with a taper toward the rear of the machine 66 slightly less than the angle between the axis of the roll and the axis of the machine. This angle is illustrated as being approximately 10, but may be varied to meet requirements. The main functions of this zone B are to grip or frictionally engage the work piece and cause it to rotate on its own axis and to feed it, longitudinally; but a secondary function is to press the wall of the tubular member against the mandrel preparatory to the main reduction that is effected by the next zone C.

Zone C is in the form of a conical shoulder which makes an angle of approximately to zone B and thus makes an angle of 60 to the axis of the machine. Thus, the apex of the conical surface of the shoulder lies in the axis of the roll near the large end thereof. The main reduction of diameter of the work piece is effected by this shoulder which constitutes zone C, the amount of such reduction being double the height of the shoulder.

The fourth zone D is in the form of a shallow groove, preferably made with a conical band 5 next to the rib and with a greater taper (say 120) than the general taper of the roll and with a second hand 6 which may be cylindrical. The main purpose of this depression is to keep the work roll free from contact with the portion of the work piece that is just past the shoulder thereby avoiding changing the peripheral speed of the work piece with consequent twisting thereof.

The fifth zone E is of conical form with an angle of taper substantially equal to the angle between the axis of the work roll and the axis of the machina-whereby the portion of its surface in contact with the work is substantially parallel with the axis of the work. This zone E has three principal functions: namely, first, to frictionally engage and rotate the work at approximately the same speed ratio as that of zone B, whereby the tendency of the work to twist is minimized; second, as in the case of zone B, it helps to feed the work piece longitudinally; and third, zone E smooths down any ridges and unevenness of surface and, in the case of tubes, rolls out any unevenness of wall thickness and causes the tube to balloon slightly so that it is loose on the mandrel and can be easily stripped therefrom.

The last zone F is a relatively narrow band which tapers toward the axis of the roll at a greater angle than zone E, whereby the tip 4 of the roll is further from the axis of the machine than the zone E. An important purpose of the zone F is to insure the roundness of the work piece, especially in the case of tubes, whose shape in cross section opposite zone E is triangular or polygonal. I

The operation of the apparatus hereinbefore described is as follows:

The end of the work piece I enters longitudinally between the zones A of the rotating rolls 2, and is frictionally engaged by the zones B thereof which feed it along and cause it to rotate on its own axis and incidentally reduce its wall thickness slightly. When the work presses against the oblique shoulders, being zone C of the work rolls, the metal is squeezed or rolled thereby to a smaller diameter, the work done by each work roll preferably overlapping. that of the next preceding. The effect of this rolling is to greatly lengthen the work piece and reduce its general diameter, leaving it out of round and with unevennesses in its periphery. When the work piece reaches zone E, the frictional engagement thereof with the work piece rotates such work piece on its axis, feeds it longitudinally, smooths its surface, and, in the case of tubes, evens up the wall thickness and slightly increases the circumference. The rearmost zones F bring the work piece to true roundness.

The foregoing description applies to the rolling of the work whether solid or tubular. In the case of tubes, the initial work piece is a pierced billet, into which a cylindrical mandrel is inserted and in which it remains throughout the rolling operation. As the taper of the rear portion E of the work rolls is the same as the angle between the axis of the mill and the axes of the rolls but closer to the axis of the mill, enough "ballooning, that is, increase in the diameter of the bore of the work, takes place at this point of the operation to permit easy removal of the mandrel from the finished tube.

It is noted that all operations on the work piece are effected in a single continuous run thereof through the mill. Consequently, my process is much more rapid than the common practice, which requires repeated runs of the work back and forth through successive passes.

It is also noted that ordinary wear and tear on the rolls used in my process can be readily compensated for merely by adjusting the position of the rolls with relation to the axis of the mill without redressing or replacing said rolls, whereas present day practice necessitates such redressing or replacement when the wear exceeds the limit of tolerance permissible for the product.

It is also noted that the effect of applying the rolling pressure helically to a pierced billet with a mandrel therein tends to correct any lack of concentricity' of its inner and outer surfaces, whereas there is often a reverse tendency in the present day common practice of applying the pressure along longitudinal lines.

While I have described the work roll with a single shoulder zone of steep angle, it is obvious that more than one such shoulder may be used.

What I 'claim is:

1. The improvement in the art of rolling rods and tubes to reduce and elongate them which consists in concentrating the working pressure on a single narrow zone of the work piece and applying such pressure to such zone by means of a skewed steeply inclined rotating surface against which the work piece is fed continuously.

2. The process of reducing and elongating rods and tubes by rolling which consists in simultaneously rotating the work piece and advancing it longitudinally through a single narrow abruptly converging roll pass comprising steeply inclined shoulders arranged at an angle to the axis of the work piece, without substantial change of diameter of such work piece before reaching such pass, whereby the work of reduction and elongation is concentrated on the narrow zone of the work piece in said pass.

3. The process of reducing and elongating rods and tubes by rolling which consists in simultaneously rotating the work piece and advancing it longitudinally without substantial change of diameter through a single roll pass whose surface is continuously steeply inclined so as to concentrate the pressures on the narrow zone of the work piecewithin said steeply inclined pass and effect uniform flow of the metal to reduce and elongate the work piece and which surface is arranged at an angle to the axis of the work piece.

4. The process of reducing and elongating rods and tubes by rolling which comprises simultaneously rotating the work piece in such manner that the unreduced and reduced portions thereof revolve at substantially the same rate and thereby avoid twisting, and feeding the work piece, longitudinally and conformably with the progress of rolling, through a single steeply converging roll pass comprising steeply inclined shoulders arranged at an angle. to the axis of the work piece, to concentrate the working pressure on a narrow zone of the work piece.

5. The process of rolling rods and tubes which comprises simultaneously rotating and longitudinally feeding the work piece to the roll pass without material reduction of the diameter thereof, reducing the diameter of the work piece by rolling pressure applied to a single narrow zone of the work piece at a steep angle and at an angle to the axis of the work piece, and reeling the reduced portion while maintaining substantially the same velocity ratio at the periphery of the reduced and unreduced portions.

6. The process of rolling rods and tubes which comprises applying driving force frictionally and in an. obliquely rearward direction to the periphery of the work forward of the reducing pass to simultaneously rotate and longitudinally feed the work without substantial reduction of the work before it reaches the pass, concentrating the reducing pressure on a single narrow band of the work piece by means of abruptly converging pass surfaces arranged at an angle to the axis of the work piece and simultaneously reeling the portion of the work beyond said pass by frictionally applying driving force obliquely and in a rearward direction to the periphery of the work at the same rotational velocity as the first mentioned force so as to prevent twisting of the work.

7. The process of rolling tubes which comprises simultaneously rotating a pierced billet in such manner that the unreduced and reduced portions thereof revolve at the same rate and thereby avoid twisting, feeding the billet longitudinally and conformably with the progress of rolling and maintaining a concentration of working pressure on a single narrow zone of the work. piece by making the rolling surfaces of the pass incline rearwardly towards the axis of the work at a steep angle and arranging them at an angle to the axis of the work piece and maintaining interior support for the wall of the billet without stretching it radially.

8. The process of reducing the diameter and wall thickness of tubes which comprises affording interior cylindrical support for a pierced billet, simultaneously rotating said billet on its axis and feeding it longitudinally, substantially limiting the working pressure to a single narrow zone of the work piece on which such pressure acts obliquely by means of an abruptly converging pass, and additionally feeding and reeling the portion of the billet that emerges from said pass.

9. The process of rolling rods and tubes which comprises feeding the work piece along the pass line by applying driving force tangentially to the periphery of the unreduced portion thereof and in a direction at an oblique angle to the axis of the work piece, thereby rotating the work piece and advancing it longitudinally without substantial expansion or reduction of the diameter thereof, reducing and elongating said work piece by concentrating the working pressure on a single narrow zone thereof to which it is applied in an oblique direction by steeply converging the pass, and additionally feeding the work piece by applying driving force tangentially to the periphery of the reduced portion of the work and in the same direction assaid first mentioned force to rotate it at substantially the same velocity ratio as that produced by the first named force.

10. The process of reducing the diameter and wall thickness of tubes which comprises affording interior support for a pierced billet, simultaneously rotating said billet on its axis and feeding it longitudinally against a rotating conical reaction surface that inclines rearwardly, substantially limiting the work of reduction to a single narrow zone of the work piece opposite said reaction surface.

11. The process of reducing the diameter and wall thickness of tubes which comprises affording interior support for a pierced billet, simultaneously rotating said billet on its axis and feeding it longitudinally against a rotating conical reaction surface that inclines rearwarkily, substantially limiting the work of reduction to a single narrow zone of the work piece opposite said reaction surface, and additionally feeding and reeling the portion of the billet that emerges from the pass.

WALTER J. ASSEL. 

